Act on is a verb which means to take action based on a particular directive or guidance. There are several synonyms for the phrase act on. These include respond, react, answer, execute, implement, carry out or obey. The word respond denotes the act of reacting to something. React implies a quick and sometimes automatic response. Answer is a synonym that often connotes a response to a question. Execute refers to putting things into action. Implement means applying or enforcing something, while obey implies a dutiful response to an authority or command. Therefore, it is important to choose the right word to convey the desired meaning when looking for synonymous words for act on.